Wii Fit Trainer is pretty what the fuck, but at the same time, Wii Sports/Play/Fit getting some sort of representation wasn't all that unlikely. I think a lot of people assumed it would, but only through Miis, not Miis and WFT.
As for Retro characters, its odd this time around. We have 3 arguably retro characters in Little Mac, Pac-man, and Mega Man. However, all have had new games in the last 5 years, unlike Pit (at the time of Brawl), Ice Climbers, R.O.B. (not counting cameos), and Mr. Game & Watch. So it's a bit different this time around. Plus, two of them are third parties, though I don't know if this would affect anything.